The present invention generally relates to filtration apparatus and, in a preferred embodiment thereof, more particularly relates to a specially configured expandable well screen assembly for use in a subterranean wellbore, and associated methods of fabricating the well screen.
It is useful in some circumstances to be able to convey generally tubular equipment into a subterranean wellbore to a predetermined location therein, and then outwardly expand the equipment in the wellbore. For example, a restriction in the wellbore may prevent the equipment in its expanded configuration from passing through that part of the wellbore, but the equipment may pass through the restriction in its retracted configuration. In one application of this principle, it is known to use expandable well screens in wellbores.
An example of the potential usefulness of expandable equipment in a wellbore is where the wellbore intersects a productive, relatively unconsolidated formation. It is desirable in many situations to be able to utilize a well screen to filter production fluid from the formation, while foregoing the expense of cementing casing in the wellbore and performing a gravel packing operation. Unfortunately, without any radial support the unconsolidated formation would likely collapse into the wellbore, causing additional expense and loss of revenue. Conventional nonexpandable well screens must necessarily be smaller than the wellbore in order to be conveyed therethrough, and so they are incapable of providing any radial support for an unconsolidated formation.
Previously proposed expandable well screens have associated therewith several problems, limitations and disadvantages. For example, they are typically not designed for contacting and providing radial support for a formation, and are thus unsuited for this purpose. Additionally, at least one previously proposed well screen assembly construction has a multi-layer configuration in which various tubular elements must be telescoped with one another and then intersecured. The relative structural complexity of this previously proposed expandable well screen assembly, and the necessity of using multiple steps to fabricate it, undesirably increases its fabrication cost. Moreover, since the assembly portion outwardly circumscribing a perforated base pipe portion of the well screen has several layers, the maximum permissible unexpanded diameter of the base pipe is undesirably reduced due to the necessity of limiting the outer diameter of the well screen assembly to a maximum value determined by limiting well dimensions. Due to this reduced unexpanded diameter of the base pipe, operational expansion thereof undesirably increases the expansion stresses thereon and reduces the maximum available expanded diameter thereof.
AS can readily be seen from the foregoing, a need exists for an improved expandable well screen, and associated fabrication methods, that eliminate or at least substantially reduce the above-mentioned problems, limitations and disadvantages of previously proposed well screen constructions as generally described above. It is to this need that the present invention is directed.